Properties of nanostructured undoped ZrO₂ thin film electrolytes by plasma enhanced atomic layer deposition for thin film solid oxide fuel cells

Abstract

Nanostructured ZrO₂ thin films were prepared by thermal atomic layer deposition (ALD) and by plasma-enhanced atomic layer deposition (PEALD). The effects of the deposition conditions of temperature, reactant, plasma power, and duration upon the physical and chemical properties of ZrO₂ films were investigated. The ZrO₂ films by PEALD were polycrystalline and had low contamination, rough surfaces, and relatively large grains. Increasing the plasma power and duration led to a clear polycrystalline structure with relatively large grains due to the additional energy imparted by the plasma. After characterization, the films were incorporated as electrolytes in thin film solid oxide fuel cells, and the performance was measured at 500 °C. Despite similar structure and cathode morphology of the cells studied, the thin film solid oxide fuel cell with the ZrO₂ thin film electrolyte by the thermal ALD at 250 °C exhibited the highest power density (38 mW/cm(2)) because of the lowest average grain size at cathode/electrolyte interface.